getdtablesize() - get descriptor table size ,注意d

NAME
       getdtablesize - get descriptor table size

SYNOPSIS
       #include <unistd.h>

       int getdtablesize(void);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       getdtablesize(): _BSD_SOURCE || _XOPEN_SOURCE >= 500

DESCRIPTION
       getdtablesize()  returns the maximum number of files a process can have open, one more than the largest possible value
       for a file descriptor.

RETURN VALUE
       The current limit on the number of open files per process.

ERRORS
       On Linux, getdtablesize() can return any of the errors described for getrlimit(2); see NOTES below.

CONFORMING TO
       SVr4, 4.4BSD (the getdtablesize() function first appeared in 4.2BSD).  It is not specified in  POSIX.1-2001;  portable
       applications should employ sysconf(_SC_OPEN_MAX) instead of this call.

NOTES
       getdtablesize()  is implemented as a libc library function.  The glibc version calls getrlimit(2) and returns the cur-
       rent RLIMIT_NOFILE limit, or OPEN_MAX when that fails.  The libc4 and libc5 versions return OPEN_MAX (set to 256 since
       Linux 0.98.4).

SEE ALSO
       close(2), dup(2), getrlimit(2), open(2)